Surgical adjuvant intravesical bacille Calmette-Guerin (BCG) is the treatment of choice for superficial transitional cell carcinoma of the bladder. Prospective randomized clinical trials have shown that the efficacy of intravesical BCG as an adjuvant to surgery is superior to surgery alone or adjuvant chemotherapy. Available data from clinical and animal model studies suggest that the development of a systemic immune response to BCG and its local expression in the bladder are essential for the therapeutic effects of intravesical BCG therapy. The attachment of BCG to the bladder wall and the subsequent initiation of immunological responsiveness appears to be dependent on fibronectin (FN). The FN/BCG interaction and its effects on BCG-mediated antitumor activity will be studied. The interaction will be modulated in an effort to enhance the antitumor activity of intravesical BCG therapy. The initial studies will characterize the binding molecules on FN and BCG. This is an essential first step which will lead to the development of reagents, eg., monoclonal antibodies, binding peptides, etc., that will allow a study of the role of FN in antitumor activity. The characterization studies will examine the interaction of BCG with isolated domains of FN, produce monoclonal antibodies against the binding domain(s) and prepare synthetic peptides that contain the BCG binding sequence. Once the FN binding site is identified, the primary area of study will be identification of the BCG binding molecule for FN. The biochemical nature of the BCG surface molecules that interact with fibronectin will be determined. The most productive approach for identifying the molecule(s) is not clear. Four possible approaches are outlined: (a) isotopically labelling of the molecules with 35-S04, 125-I, 32-P04, and/or 14-C leucine; (b) monoclonal antibodies to BCG cell surface antigens; (c) crosslinking FN or FN peptides to BCG; (d) examing BCG culture supernatants for FN binding activity. The reagents developed above will be used to definitively characterize the role of the BCG/FN interaction in the antitumor response. Our efforts will focus on two primary areas of activity: (a) augmentation of immunological responses through modulation of phagocytosis, antigen processing and presentation and bactericidal activity. Also, the potential for the development of autoimmune reactivity to FN will be tested including humoral and cell-mediated responses. (b) The role of FN as a binding matrix. The effects of anti-FN antibodies. FN peptides and antiBCG antibodies on BCG binding and the subsequent development of immunological responses to BCG and antitumor activity will be studied. Finally, we will attempt to modulate the BCG/FN interaction in an effort to enhance antitumor activity.